The article “Energy-selective Reconstructions in X-ray Computerized Tomography” by Alvarez and Macowski, Phys. Med. Biol, Vol. 21, No. 5, pages 733-744 (1976) discloses that a computed tomography system comprising a radiation source emitting polychromatic radiation and an energy-resolving detector for generating projection data being indicative of the radiation after having traversed the object. The projection data are acquired while the radiation source and the object move relative to each other, in order to acquire projection data in different projection directions. A component decomposition technique is applied to the acquired projection data, in order to determine photoelectric effect attenuation values and Compton effect attenuation values, which are caused by the photoelectric effect and the Compton effect, respectively. The photoelectric effect attenuation values are backprojected for generating a photoelectric effect image of the object and the Compton effect attenuation values are backprojected for generating a Compton image of the object.
The photoelectric effect image and the Compton effect image are corrupted by noise and have therefore a reduced image quality.